This invention relates generally to the field of unmanned aerial vehicles, commonly referred to as drones.
The use of drones in commercial or recreational applications has increased dramatically in recent years, primarily due to the development of improved flight and power systems. Drones may be free flying, such that power is supplied by onboard batteries and flight instructions are delivered to the drone through wireless communications, or tethered, such that power and/or flight instructions are delivered through the tether connecting the drone to ground equipment or ground vehicles.
Free flight drones have limited flight duration, since all power is supplied by onboard batteries, typically in the form of multi-cell battery packs. The storage capacity and number of batteries is limited by size and weight restrictions. Often, flight time is limited to about 20 minutes or less, and may be decreased by external factors such as wind, which may reduce flight to less than about 8 minutes. Thus, the use of free flight drones for long time periods requires frequent landing and recharge/replacement of the batteries.
In situations where the drones are relatively stationary when aloft, or where ground vehicles can travel in tandem with moving drones, the use of tethered drones solves the battery problem. In a tethered drone, the primary power supply is located on the ground, either as stationary equipment or on a vehicle. Stationary equipment may comprise one or more large batteries, batteries recharged by a generator, power directly produced by the equipment (AC converted to DC), or power derived from direct connection to a utility grid with conversion to DC. Vehicles may comprise one or more large batteries, batteries recharged by a vehicle-mounted generator, or power directly produced on the vehicle (AC converted to DC). Thus, the flight duration of tethered drones may be dramatically increased in comparison to free flight drones, to the point of being continuous. There is no need to interrupt the operation of the drone in order to recharge onboard batteries.
Because the tethered drones are much more advantageous in many applications, some manufacturers of free flight drones have taken steps to preclude removal or bypassing of the onboard batteries with connection of the operational systems of the drone directly to ground-sourced power in order to convert free flight drones to ground-powered tethered drones. For example, some free flight drone companies provide a closed system with custom software which utilizes encrypted communication between the battery circuit board of the onboard battery pack and the drone main circuit board, the encryption being hash keyed and dynamically generated. The battery circuit board communicates battery condition to the vehicle main board, including authentication messages; monitors battery cell status; charge controls individual cells; and executes logic related to cell use time, overall battery life expectancy, and a number of other statuses. The safeguards prevent operation of the free flight drone if the batteries are removed or if an alternate (ground-based) power source is provided.
It is an object of this invention to provide a system and method for converting free flight drones to tethered drones that overcomes the impediments designed into certain free flight drones, wherein the system allows power to be supplied to the drone from a ground-based power supply through a tether connected to the drone. It is a further object to provide such a system and method wherein drones that are safeguarded against removal of batteries or use of an alternate power supply may be converted. It is a further object to provide such a system and method wherein emulated signals are delivered to the battery circuit board of the drone for communication with the main circuit board, such that the main circuit board believes the drone is being powered by properly charged batteries instead of a ground-based power supply.